An Iranian tanker held by Gibraltar since July after being the center of a diplomatic dispute has left port, and is heading to the Greek island of Kalamata, marine tracking data showed on Monday.

The trail left by GPS data on Marinetraffic.com, a vessel tracking service, showed the Iran-flagged Adrian Darya 1, previously known as Grace 1, moving shortly before midnight on Sunday. Its destination was not immediately clear until Monday.

Iran’s ambassador to Britain, Hamid Baeidinejad, had written on Twitter earlier that the vessel was expected to leave on Sunday night, adding that two engineering teams had been flown to Gibraltar.